“My Mac used to be fast, but now it’s running so slow.” I’ve heard many versions of this complaint, and they’re always factually true, not just opinions: Macs do become sluggish over time, even if all of their chips and hard drives are working like new.

I’ve devoted several columns to hardware solutions — replacing old hard drives with fast new SSDs, adding more RAM, and increasing storage capacity using an external drive — but there are software solutions, too. Even die-hard Apple fans will admit that Macs typically run new OS X versions better (faster, and with fewer bugs) if you start with a clean slate: completely wipe your hard drive, do a fresh install of the latest OS X release, and restore only the files you need. That’s not as hard as it sounds, but it’s a radical and fairly time-consuming solution.

This How-To article offers a simpler alternative. First, find and delete enough files to leave your Mac at least 50GB of free storage capacity — enough room for the Mac to work without pausing to manage its hard drive space. Next, cleanse the cruft OS X builds up in the background as you use your computer. Below, I’ll show you how two completely free Mac programs, GrandPerspective and OnyX, will do all the heavy lifting for you. GrandPerspective offers a highly visual display of what’s taking up space on your Mac; Onyx cleans up the Mac files you’d be afraid to touch yourself…